1. Field of the Invention
The present invention relates to an inspection method and an inspection apparatus, particularly, to an inspection method and an inspection apparatus which permit suppressing the needle pressure applied by a probe to the inspection electrode of a target object to be inspected.
2. Description of the Related Art
In the manufacturing process of semiconductor devices, these devices are formed on a semiconductor wafer. Then, inspected are the electrical characteristics of the target object(s) to be inspected (hereinafter referred to as “the device”) such as a device in the state of the semiconductor wafer and a device cut away from the semiconductor wafer and packaged. In the inspection process, the device is inspected by transmitting and receiving an electric signal to and from a tester via a probe electrically in contact with the inspection electrodes of the device.
Where the inspection electrode is formed of a material that is likely to be oxidized such as aluminum, copper or a solder, an insulating film such as an oxide film is formed on the surface of the inspection electrode in the inspecting stage. Therefore, even if the probe is brought into contact with the inspection electrode, the electrical connection between the two is not stabilized. Particularly, where the inspection electrode is made of aluminum, a very hard oxide film is formed on the surface of the inspection electrode, with the result that it is very difficult to bring the probe into electrical contact with the inspection electrode.
In the prior art, the probe is brought into electrical contact with the inspection electrode by the mode shown in FIGS. 22A and 22B in accordance with the flow chart shown in FIG. 21. Specifically, the preparation for the inspection of the device is performed first (step S1), followed by bringing the probe N into contact with the inspection electrode P with a predetermined pressure, e.g., 10 to 20 g/a probe, as shown in FIG. 22A (step S2). Then, it is judged whether or not the probe N has been brought into electrical contact with the inspection electrode P (step S3). Where it is judged that electrical contact has been achieved, the inspection is started (step S4). In general, it is judged in step S3 that the probe N is not in electrical contact with the inspection electrode P by simply bringing the probe N into contact with the inspection electrode P because an insulating film O is interposed between the two. In order to overcome the difficulty, the probe N and the inspection electrode P are reciprocated relative to each other (scrubbed) as denoted by an arrow in FIG. 22B so as to scrape off the insulating film O (step S5). In this step S5, the probe N is brought into electrical contact with the inspection electrode P. After electrical contact has been confirmed, the inspection is started in step S4.
Another method of breaking the insulating film O is to sharpen the tip of the probe. In this method, it is possible to increase the planar pressure given by the probe to the inspection electrode, making it possible to permit the probe to be stuck into the inspection electrode so as to ensure a good electrical contact between the two. In this case, it is necessary to stick the tip of the probe into the inspection electrode by at least 2,000 to 4,000 Å in order to ensure electrical contact.
Recently, proposed is a probe card having fine probes each having a diameter of scores of microns formed in a silicon substrate with a small pitch by using, for example, micro machine processing technology. Since the probe card has a micro structure, it is possible for the probe card to cope with a high speed signal. In addition, since the probe is formed on a silicon substrate, the probe card is advantageous in that it eliminates the effects caused by the difference in the thermal expansion coefficients of the probe card and the device in the heating test.